Method and system for removal of gas and plasma processing apparatus

ABSTRACT

A gas removal system that removes a halogen gas remaining inside a processing chamber after executing a specific type of processing inside the processing chamber maintained in an airtight state with plasma obtained through discharge dissociation of the halogen gas supplied from a gas supply device comprises a pressure control device that controls the pressure inside the processing chamber, an air supply device that supplies the atmospheric air into the processing chamber after the pressure inside the processing chamber is lowered by the pressure control device, a control device that controls the air supply device and an evacuation device that evacuates a gas produced through a reaction of the halogen gas and the atmospheric air having occurred inside the processing chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase application based onPCT/JP01/10714, filed Dec. 7, 2001, the content of which is incorporatedherein by reference, and claims the priority of Japanese PatentApplication no. 2000-374438, filed Dec. 8, 2000, the content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gas removal method, a gas removalsystem and a plasma processing apparatus that are ideal in applicationsin which plasma processing is executed with a gas containing halogen (ahalogen gas).

2. Description of the Related Art

Plasma processing apparatuses that execute plasma processing by using ahalogen gas such as a chlorine-based gas are utilized in the field ofsemiconductor production in the related art. During an etching processexecuted by using a chlorine-based gas, a chlorine-based reactionproduct becomes deposited at the inner wall surfaces of the processingchamber and internal members constituting the processing apparatus andthe etching process is adversely affected by the chlorine-based reactionproduct deposit. For this reason, it is necessary to regularly clean theinside of the processing chamber with an organic solvent such asalcohol. However, the chlorine-based gas, as well as the chlorine-basedreaction product, is present inside the processing chamber immediatelyafter the process and it is dangerous to open the processing chamber insuch a state.

Accordingly, the chlorine-based gas is removed while maintaining theprocessing chamber in an airtight state in the related art. When theatmospheric air and N2 are supplied into the processing chamber in asealed state, the chlorine-based gas is transformed to acid by themoisture contained in the atmospheric air. By evacuating this acidthrough an acid evacuation line, the chlorine-based gas is removed fromthe processing chamber. Only after the chlorine-based gas is removed asdescribed above and safety is thus assured, the processing chamber isopened to the atmosphere for cleaning.

However, since the atmospheric air and N2 are supplied into the sealedprocessing chamber, there is a limit to the quantities of atmosphericair and N2 that can be taken in and it takes a considerable length oftime to supply the atmospheric air and N2 and to transform thechlorine-based gas to acid in the related art described above. It takesas long as approximately 300 minutes to lower the chlorine-based gasconcentration to the level at which the processing chamber can be safelyopened, i.e., under 2 ppm, in a standard plasma processing apparatus, tolead to an increase in the down time of the apparatus and a pooroperating rate.

SUMMARY OF THE INVENTION

An object of the present invention, which has been completed byaddressing the problems of the related art discussed above, is toprovide a new ad improved gas removal method and a new and improved gasremoval system that make it possible to reduce the length of timerequired to remove the halogen gas in the processing chamber and aplasma processing apparatus adopting the gas removal method and the gasremoval system.

In order to achieve the object described above, in a first aspect of thepresent invention, a gas removal method for removing a halogen gasremaining in a processing chamber after executing a specific type ofprocessing inside the processing chamber in an airtight state withplasma obtained through discharge dissociation of the halogen gas,comprises a step in which the pressure inside the processing chamber isreduced to a level lower than the atmospheric pressure, a step in whichatmospheric air is supplied into the processing chamber and a step inwhich a gas produced through a reaction of the halogen gas and theatmospheric air having occurred inside the processing chamber isevacuated.

By adopting this gas removal method in which the pressure inside theprocessing chamber is reduced to a level that is at least lower than theatmospheric pressure (reduced to a negative pressure), the gas is notallowed to become diffused to the outside of the processing chamber whenthe atmospheric air is supplied into the processing chamber. Inaddition, since the pressure inside the processing chamber is sustainedat a low level, the atmospheric air can be supplied with ease. As aresult, the reaction product resulting from the reaction of the suppliedatmospheric air and the gas present in the processing gas can beevacuated to achieve fast and reliable gas removal. Furthermore, sincethe pressure inside the processing chamber is sustained at a negativelevel, there is no irritating odor of the gas and the gas leakagedetector does not go off during the subsequent maintenance work, therebyassuring safety of the maintenance personnel.

It is desirable that the atmospheric air be supplied into the processingchamber by using a supply path through which the process gas used forthe plasma processing is supplied into the processing chamber. Since theprocess gas supply device used to supply the process gas for the plasmaprocessing and the system utilized to supply the atmospheric air intothe processing chamber can be partially integrated in this manner, thegas can be evacuated through a simpler structure. In addition, since alarge drive system is not required, the gas removal can be automatedwith ease.

Moreover, during the step in which the atmospheric air is supplied intothe processing chamber, the processing chamber may be opened to theatmosphere. Since the atmospheric air can be taken in a large quantityby opening the processing chamber to the atmosphere, the length of timerequired for the gas removal can be greatly reduced.

The halogen gas may be a chlorine-based gas such as chlorine or it maybe a bromine-based gas such as hydrogen bromide.

In order to achieve the object described above, a gas removal systemthat removes a halogen gas remaining inside a processing chamber afterexecuting a specific type of processing inside the processing chamber inan airtight state with plasma obtained through discharge dissociation ofa process gas containing the halogen gas supplied from a process gassupply device comprising a pressure control device that controls thepressure inside the processing chamber, an air supply device thatsupplies atmospheric air into the processing chamber after lowering thepressure inside the processing chamber with the pressure control device,a control device that controls the air supply device and an evacuationdevice that evacuates a gas produced through a reaction of the halogengas and the atmospheric air having occurred in the processing chamber isprovided in a second aspect of the present invention.

By adopting this gas removal system in which the pressure inside theprocessing chamber is reduced to a level that is at least lower than theatmospheric pressure (reduced to a negative pressure), the gas is notallowed to become diffused to the outside of the processing chamber whenthe atmospheric air is supplied into the processing chamber. Inaddition, since the pressure inside the processing chamber is sustainedat a lower level, the atmospheric air can be supplied with ease. As aresult, the reaction product resulting from the reaction of the suppliedatmospheric air and the gas present in the processing gas can beevacuated and the gas can be removed promptly with a high degree ofreliability. In addition, since the pressure inside the processingchamber is sustained at a negative level, there is no irritating odor ofthe gas and the gas leakage detector does not go off during thesubsequent maintenance work, thereby assuring safety of the maintenancepersonnel.

It is desirable that the air supply device supply the atmospheric airinto the processing chamber via a supply port through which the processgas is supplied by the process gas supply device into the processingchamber or that a supply path through which the process gas is suppliedinto the processing chamber by the process gas supply device bepartially shared by the gas supply device. Since this achieves a partialintegration of the process gas supply device which supplies the processgas for the plasma processing and the air supply device which suppliesthe atmospheric air into the processing chamber, the gas can beevacuated through a simple structure. In addition, since a large drivesystem is not required, the gas removal system can be automated withease.

Alternatively, the air supply device may supply the atmospheric air intothe processing chamber via a supply port other than the supply portthrough which the process gas is supplied into the processing chamber bythe air supply device. By adopting such a structure, too, the gas can bepromptly removed with a high degree of reliability, and since a largedrive system is not required, the gas removal system can be automatedwith ease.

Furthermore, the air supply device may comprise an atmosphere openingdevice that opens the processing chamber to the atmosphere. Since theatmospheric air can be taken in large quantity into the processingchamber by providing such an atmosphere opening device, the length oftime required for the gas removal can be greatly reduced.

The atmosphere opening device may comprise a rotating mechanism for theprocess gas supply device. By opening the processing chamber to theatmosphere by utilizing the rotating mechanism of the process gas supplydevice, the gas removal system can be achieved without having to greatlymodify the structure of the processing apparatus.

It is desirable that a sensor which detects the extent to which theprocessing chamber is open to the atmosphere by the means for atmosphereopening be provided to facilitate the gas removal control.

As an example, the gas removal control achieved by utilizing the sensormay adopt the following structure. Namely, the processing chamber may beopened to the atmosphere by the means for atmosphere opening to a firstdegree at which the processing chamber is not opened to the atmosphereat all, a second degree at which the processing chamber is opened to theatmosphere to a predetermined extent to remove the gas or a third degreeat which the processing chamber is completely opened to the atmosphere,and the sensor may comprise a first sensor having a detection range fromthe first degree to the second degree and a second sensor having adetection range from the second degree to the third degree.

This structure facilitates verification of the state of the processingchamber by using the first sensor and the second sensor, i.e., if theprocessing chamber is in a fully closed state, if the process of gasremoval is in progress at the processing chamber or if the processingchamber is in a fully open state. For instance, a light emitting diodemay emit light in response to a signal provided by the first or secondsensor to alert the operator to the state of the processing chamber andthe means for atmosphere opening.

The degree to which the processing chamber is open to the atmosphere forgas removal (the second degree) should be set to, for instance,approximately 2% of the degree at which the processing chamber iscompletely open (the third degree). It is to be noted that the seconddegree does not need to be fixed at 2% of the third degree, and it canbe adjusted in correspondence to the pressure inside the processingchamber. Namely, the extent to which the processing chamber is open tothe atmosphere during gas removal can be increased as the pressureinside the processing chamber becomes lower.

In addition, it is desirable that the means for atmosphere opening issuea warning if the first sensor detects that the extent to which theprocessing chamber is open to the atmosphere is the first degree beforea predetermined length of time elapses. The predetermined length of timein this case refers to the length of time that must elapse before a gasconcentration level at which the processing chamber can be opened safelyis achieved following a gas removal executed through the gas removalsystem according to the present invention. By issuing a warning if theprocessing chamber enters the fully closed state (i.e., if the firstsensor detects that the processing chamber is open to the atmosphere tothe first degree) before the gas concentration level at which theprocessing chamber can be safely opened is achieved, an efficient gasremoval is assured.

Moreover, it is desirable that the means for atmosphere opening issue awarning if the second sensor detects that the extent to which theprocessing chamber is open to the atmosphere is the third degree beforea predetermined length of time elapses. The predetermined length of timein this case refers to the length of time that must elapse before a gasconcentration level at which the processing chamber can be opened safelyis achieved following a gas removal executed through the gas removalsystem according to the present invention. By issuing a warning if theprocessing chamber enters the fully open state (i.e., if the secondsensor detects that the processing chamber is open to the atmosphere tothe third degree) before the gas concentration level at which theprocessing chamber can be safely opened is achieved, any leakage of thegas is prevented and the safety of the chlorine-based gas removalprocess is increased.

The halogen gas may be a chlorine-based gas such as chlorine or it maybe a bromine-based gas such as hydrogen bromide.

In addition, the present invention provides a plasma processingapparatus employed to execute plasma processing on a workpiece inside aprocessing chamber, which removes the gas inside the processing chamberby utilizing the gas removal system achieving outstanding advantages asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a plasma processing apparatus;

FIG. 2 schematically illustrates the processing apparatus achieved in afirst embodiment;

FIG. 3 illustrates the structure adopted in an upper electrode rotatingmechanism;

FIG. 4 illustrates sensor detection ranges;

FIG. 5 illustrates the sequence of the gas removal processing;

FIG. 6 shows the relationship between the length of the gas removal timeand the gas concentration;

FIG. 7 schematically illustrates the plasma processing apparatusachieved in a second embodiment; and

FIG. 8 schematically illustrates the plasma processing apparatusachieved in a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed explanation of the preferred embodiments ofthe gas removal method, the gas removal system and the plasma processingapparatus according to the present invention, given in reference to theattached drawings. It is to be noted that in the specification and thedrawings, the same reference numerals are assigned to componentsachieving substantially identical functions and structural features topreclude the necessity for a repeated explanation thereof. It is to bealso noted that the term “halogen gas” used in the description of thepresent invention specifically refers to a chlorine-based gas such asCl₂ or a bromine-based gas such as HBr (hydrogen bromide) that is likelyto generate a hazardous substance when it reacts mainly with theatmospheric air. The following explanation is given on the assumptionthat a chlorine-based gas such as Cl₂ is used.

(Basic Structure of Plasma Processing Apparatus)

First, in reference to FIG. 1, the basic structure of a plasmaprocessing apparatus 100 according to the present invention isexplained.

A processing chamber 102 of the plasma processing apparatus 100 isformed inside an airtight and electrically conductive processingcontainer 104. An electrically conductive lower electrode 106 isprovided inside the processing chamber 102. The lower electrode 106 alsofunctions as a stage on which a workpiece such as a semiconductor wafer(hereafter referred to as a “wafer” W is placed.

In addition, an electrostatic chuck 112 is provided at the surface ofthe lower electrode 106 on which the workpiece is placed. When a high DCvoltage is applied to the electrostatic chuck 112, it firmly holds thewafer W placed on the chuck surface. In addition, an insulating ringbody 116 is provided at the lower electrode 106 so as to enclose thewafer W placed on the electrostatic chuck 112. A baffle plate 120 isprovided via an insulating member 118 around the lower electrode 106.

An elevator shaft 122 is connected to the lower electrode 106 via anelectrically conductive member 124 and the insulating member 118. Thus,the lower electrode 106 is made to move upward/downward as a drivemechanism (not shown) connected to the elevator shaft 122 engages inoperation. In addition, a bellows 126 constituted of an electricallyconductive and airtight member capable of expanding and contracting andan electrically conductive bellows cover 128 are provided around theelevator shaft 122. The bellows 126 and the 128 are each connected tothe electrically conductive member 124 and the bottom of the processingcontainer 104 at the two ends.

An upper electrode 134 is also provided inside the processing chamber102 so as to face opposite the mounting surface of the lower electrode106 on which the workpiece is placed. The upper electrode 134 alsoconstitutes part of a process gas supply device 200 that supplies aprocess gas used to execute a specific type of processing with plasma.At the outlet-side end of the process gas supply device 200, i.e., atthe portion of the upper electrode 134 facing the internal space of theprocessing chamber, numerous gas outlet holes 134 a are formed tofunction as process gas supply ports. In addition, a chlorine-based gassupply system 208 or the like that supplies, for instance, achlorine-based gas such as Cl₂ is connected to the gas outlet holes 134a.

The chlorine-based gas supply system 208 is connected with achlorine-based gas supply source 206 from which the chlorine-based gasis supplied via a switching valve 202 and a flow-regulating valve 204.

A magnet 136 is provided outside the side wall of the processing chamber102. The magnet 136 is capable of forming a rotating magnetic fieldbetween the upper electrode 134 and the lower electrode 106.

It is to be noted that components that do not bear direct relevance tothe present invention are not mentioned in the explanation given inreference to FIG. 1. In addition, the present invention is not limitedto the plasma processing apparatus 100 described above and it may beadopted in all types of processing apparatuses. For instance, it may beadopted in a plasma etching apparatus with no magnet or a plasma etchingapparatus in which high-frequency power is applied to the lowerelectrode alone (or the upper electrode alone).

Next, three embodiments of the halogen gas removal system and, morespecifically, the air supply device, that characterizes the presentinvention are explained.

(First Embodiment)

Now, the first embodiment of the present invention is explained. Thisembodiment is characterized in that an atmosphere opening device foropening the processing chamber 102 to the atmosphere is included toconstitute the air supply device of the chlorine based gas removalsystem utilized to remove the chlorine based gas from the processingchamber 102. Namely, as shown in FIG. 3, which presents an enlargementof the essential portion of the plasma processing apparatus in FIG. 2, arotating mechanism 135 that rotates the upper electrode 134 is providedas the atmosphere opening device used to open the processing chamber 102to the atmosphere. The rotating mechanism 135 is capable of freelyrotating the upper electrode 134 around a support shaft 135 a.

FIG. 4 shows the relationship between the rotating angle of the upperelectrode 134 to which the upper electrode 134 is caused to rotate bythe rotating mechanism 135 shown in FIG. 3 and the sensors utilized todetect the rotating angle. In order to improve the control, two sensors(a first sensor and a second sensor) are used in combination in theembodiment.

-   1) The detection range of the first sensor is θ0 (the processing    chamber is fully closed: 0°)˜θ2 (the gas removal position:    approximately 2°). The first sensor judges that the processing    chamber is closed when the angle to which the upper electrode 134 is    rotated by the rotating mechanism 135 is equal to or smaller than a    threshold value θ1 (approximately 1°) and judges that the processing    chamber is in an open state when the rotating angle is equal to or    greater than θ1. When the rotating angle achieved by the rotating    mechanism 135 is within the range of θ1 (approximately 1°)˜θ2 (the    gas removal position: approximately 2°) and thus, the processing    chamber is determined to be in an open state, the first sensor    outputs a processing chamber open signal S1 to a control unit 160.    It is to be noted that the first sensor constitutes a component that    characterizes the embodiment and is a new sensor which is not used    in processing apparatuses in the related art.-   2) The second sensor is the type of sensor provided in standard    processing apparatuses. The detection range of the second sensor is    θ2 (the gas removal position: approximately 2°)˜θ4 (the processing    chamber is fully open: over 90°). The second sensor judges that the    processing chamber is closed when the angle to which the upper    electrode 134 is rotated by the rotating mechanism 135 is equal to    or smaller than a threshold value θ3 (approximately 45°) and judges    that the processing chamber is in an open state when the rotating    angle is equal to or greater than θ3. Thus, the gas removal position    (θ2= approximately 2°) is set to approximately 2% of the position    corresponding to the fully open state of the processing chamber (θ4=    over 90°). When the rotating angle achieved by the rotating    mechanism 135 is within the range of θ3 (approximately 45°)˜θ4 (the    processing chamber is fully open: 90°) and thus, the processing    chamber is determined to be in an open state, the second sensor    outputs a processing chamber open signal S2 to the control unit 160.

In order to remove the chlorine-based gas, N2 is supplied in addition tothe atmospheric air. N2 is supplied into the processing chamber 102through an N2 supply line 140. The pressure of the N2 is controlledthrough a pressure switch 142 provided at the N2 supply line. An N2supply piping 144 is coated with Teflon for rust prevention.

The chlorine-based gas in the processing chamber 102 is removed bysupplying N2 and atmospheric air into the processing chamber 102 andcausing a reaction between the moisture in the atmospheric air and thechlorine-based gas. Acid produced through the reaction of the moisturein the atmospheric air and the chlorine-based gas is then evacuatedthrough an acid evacuation line 150. The evacuation pressure is achievedby the negative pressure of the suction force applied for plant acidremoval. An acid evacuation-side SUS piping 152 is coated with Teflonfor rust prevention.

Two air operation valves (a front-stage air operation valve 154 and arear-stage air operation valve 156) that are heated with a heater aremounted side-by-side onto the acid evacuation line 150. Thespecifications of these air operation valves 154 and 156 are as follows.

-   -   150° C. self temperature control (control range: 130˜170° C.)    -   power consumption: 72 W, 100V×2    -   capable of outputting an alarm when the temperature deviates        from the control range or a disconnection occurs, power is cut        off at a thermal fuse when the temperature rises to an abnormal        level

It is to be noted that they are set in an ON state at all times since ittakes 0.5˜1 hour before the temperature becomes stable.

The front-stage air operation valve 154 and the rear-stage air operationvalve 156 are controlled through different methods. Refer to theexplanation of the control sequence provided later.

-   -   special quadruple-mount type solenoid valves are provided as a        new feature

The control unit 160, which is connected to a power supply 180, controlsthe power supply to the air operation valves 154 and 156 (S11 and S16)and also implements specific control by using various signals includingheater temperature control error detection signal (S13 and S14) inputfrom the air operation valves 154 and 156 and ON/OFF signals (S12 andS15). In addition, the processing chamber open signal S1 from the firstsensor, the processing chamber open signal S2 from the second sensor, anatmospheric air signal S3 from a convectron and a roughing evacuationstart signal S4 are input to the control unit 160. In response to thesignals S1˜S4, the control unit 160 turns on/off or blinks the lightemitting diodes to alert the operator to a specific state.

A green light emitting diode (green LED 191) is turned on when theprocessing chamber can be opened. A yellow light emitting diode (yellowLED 192) flashes when the apparatus has entered a standby state for anacid evacuation count start and is turned on while the acid evacuationcount is in progress. A red light emitting diode (red LED 193) is turnedon when the processing chamber cannot be opened. A white light emittingdiode (white LED 194) flashes when the heater temperature is out of thecontrol temperature range and is turned on when the heater temperatureis at a normal level.

The gas removal method achieved in the plasma processing apparatus 100adopting the gas removal system described above is now explained. FIG. 4shows the sequence of the gas processing. In addition, FIG. 5 presents agraph of the relationship between the length of the gas removal time andthe gas concentration.

1) Atmospheric Air Detection

When the atmospheric air signal S3 provided by the convectron isdetected, both the front-stage air operation valve 154 and therear-stage air operation valve 156 are opened. Since the processingchamber 102 is still closed at this point, a slight negative pressure isgenerated inside the processing chamber 102 due to the plant acidremoval suction force. The yellow LED 192 starts to blink when theatmospheric air is detected to notify the operator that the apparatushas entered a standby state for a gas removal count start.

2) Count Start

As the upper electrode is moved to a specific position (the gas removalposition θ2) while the yellow LED 192 is blinking, the processingchamber open signal S1 from the first sensor is detected and the countof the gas removal time starts. At this point, the yellow LED 192 whichhas been blinking enters a steady ON state to notify the operator thatthe gas removal count is in progress. It is to be noted that the lengthof time to elapse between “1) Atmospheric air detection” and “2) Countstart” may be set freely by the operator.

3) During Gas Removal Count

During the gas removal process, the length of which has been preset, thegas inside the processing chamber 102 is evacuated. During this process,the red LED is on (indicating that the processing chamber 102 cannot beopened to the atmosphere) and the yellow LED is on (indicating that thegas removal count is in progress). In the graph shown in FIG. 5, the gasconcentration goes under 5 ppm when 180 minutes elapses and it fallssubstantially to 0 ppm when 240 minutes elapses. Accordingly, it isrecommended that the gas removal be executed for 240 minutes or more.However, it has been confirmed that through continuous evacuation, thegas concentration can be lowered to an acceptable level of less than 2ppm within 180 minutes.

4) The Processing Chamber Opened to the Atmosphere During the Count

If the processing chamber is opened to the atmosphere while the gasremoval count is in progress (if the processing chamber open signal S2from the second sensor is detected), the rotating mechanism 135 for theupper electrode 134 issues a warning to alert the operator. Since fullyopening the processing chamber during the gas removal count is strictlydue to an operating error, it is assumed that the operator promptlycloses the processing chamber in response to the warning. Thus, the gasremoval timer continues to count the time elapsing during this erroneousoperation.

5) The Processing Chamber Closed During the Count

If the processing chamber becomes closed during the gas removal count(if the processing chamber open signal from the first sensor is notdetected), the rotating mechanism 135 of the upper electrode 134 issuesa warning to alert the operator. However, unlike in the state describedin 4), the processing chamber may become completely closed during thegas removal count out of necessity (there is a possibility that theprocessing chamber may remain in a closed state over an extended periodof time) and, accordingly, the gas removal timer count becomestemporarily halted while the processing chamber is in a closed state.The count is resumed when the upper electrode is moved back to the gasremoval position (θ1) (when the processing chamber open signal S1 fromthe first sensor is detected). It is to be noted that since the twovalves remain open while the count is temporarily halted, the pressureinside the processing chamber is sustained at a negative level and, forthis reason, the chlorine-based gas is not allowed to flow out of theprocessing chamber when the processing chamber is opened to theatmosphere again.

6) End of the Preset Length of Time

7) Maintenance Start

When the gas removal count reaches the preset length of time, the greenLED 191 is turned on (the yellow LED 192 and the red LED 193 becometurned off) to indicate that the processing chamber can be opened to theatmosphere and thus the maintenance work can be initiated. It is to benoted that the length of time to elapse between “6) End of the presetlength of time” and “7) Maintenance start” may be freely set by theoperator.

8) During the Maintenance

Since the two valves remain in an open state during the maintenancework, a down flow is created inside the processing chamber to preventthe residual chlorine-based gas from flowing out toward the operator.

9) Closing the Processing Chamber Completely During Maintenance

If the processing chamber becomes fully closed (due to a temporary haltto the maintenance work or the like) during the maintenance process, thefront-stage air operation valve 154 alone is closed in preparation for aroughing start (so as to prevent a backward flow of the gas from theplant acid removal line at the start of the roughing process. If theprocessing chamber is opened again without starting a roughing process,the front-stage air operation valve 154 is opened again and theoperation returns to the maintenance mode described in 8) above.

10) Maintenance End

As the maintenance work is completed and the processing chamber is setin a fully closed state (θ0) in preparation for a roughing start, thefront-stage air operation valve 154 alone is closed prior to the startof the roughing process. This state is identical to the state describedin 9) above.

11) Roughing Start

Upon detecting the roughing start signal S4, the rear-stage airoperation valve 156, too, becomes closed. Since the front-stage airoperation valve 154 has been in a closed state prior to this time point,the gas is not allowed to flow back into the processing chamber throughthe plant acid removal line. In response, the green LED 191 is turnedoff and the red LED 193 is turned on (to indicate that the processingchamber 102 cannot be opened to the atmosphere). It is to be noted thatthe length of time to elapse between “10) Maintenance end” and “11)Roughing start” may be set freely by the operator.

In addition, if the upper electrode is at the gas removal position (θ2)(if the processing chamber open signal S1 from the first sensor isdetected) when the maintenance work is completed and the roughing startsignal S4 is detected, the second sensor may erroneously assume that theupper electrode at the gas removal position θ2 is at the “closed”position and, as a result, the roughing process may start while theprocessing chamber is still open to the atmosphere. For this reason, ifthe upper electrode is at the gas removal position (θ2) when theroughing start signal S4 is detected, a pseudo open signal is providedto the second sensor. Then, after the processing chamber becomes fullyclosed (θ0), the roughing process is started.

If an error occurs in the temperature control system for the airoperation valves 154 and 156 (if the heater temperature deviates fromthe control temperature range) in any of the steps taken during thesequence, the white LED 194 blinks (it remains on in a normal state).However, the gas removal sequence itself is not affected at all due to aforcible interruption or the like.

As explained above, in the embodiment in which the pressure inside theprocessing chamber 102 is reduced to a level which is at least lowerthan the atmospheric pressure (a negative pressure), the chlorine-basedgas is not allowed to become diffused into the atmosphere even when theprocessing chamber 102 is open to the atmosphere. Thus, by opening theprocessing chamber 102 to the atmosphere, the atmospheric air can betaken in a large quantity. Since a large quantity of atmospheric air canbe taken in by opening the processing chamber 102 to the atmosphere, thelength of time required to produce acid through a reaction of theatmospheric air and the chlorine-based gas to remove the chlorine-basedgas can be greatly reduced. In other words, while it takes approximately300 minutes to achieve a chlorine-based gas concentration of less than 2ppm at which the processing chamber can be opened safely in the relatedart, it becomes possible to remove the chlorine-based gas in 180 minutesor less through continuous evacuation.

In addition, since the processing chamber 102 can be opened to theatmosphere by using the rotating mechanism 135 of the upper electrode134, the structure of the apparatus does not need to be modifiedgreatly.

Furthermore, since a locking mechanism that locks the atmosphere openingdevice when the pressure inside the processing chamber is equal to orhigher than a predetermined level is provided, any leakage of thechlorine-based gas is prevented and thus, the safety of the maintenancework can be increased.

Moreover, better control is achieved with two sensors, the first sensorand the second sensor.

While the rotating mechanism 135 issues a warning for the operator ifthe processing chamber becomes open to the atmosphere or becomes closedwhile a gas removal count is in progress in the embodiment describedabove, the present invention is not limited to this example. Forinstance, the upper electrode 134 may be locked at a fixed position soas to disallow rotation thereof during a gas removal count to ensurethat the processing chamber does not become opened to the atmosphere orcompletely closed off.

In addition, the processing chamber may be determined to have beenopened to the atmosphere during a gas removal count when the upperelectrode 134 is set to the full open position (θ4) or when it isdecided that the processing chamber is in an open state (θ3)˜(θ4).Likewise, the processing chamber may be determined to have beencompletely closed when the upper electrode 134 is set to the full closedposition (θ0) or when it is decided that the processing chamber is in aclosed state (θ0)˜(θ1).

(Second Embodiment)

Next, the second embodiment of the present invention is explained. Thisembodiment is characterized in that the air supply device is constitutedof a device that supplies a gas to be used for chlorine-based gasremoval into the processing chamber 102 through the supply ports throughwhich the process gas used in the plasma processing executed in theprocessing chamber 102 is supplied, i.e., through the gas outlet holes134 a in this example, instead of the atmosphere opening device in thefirst embodiment. Namely, the supply paths for the process gas and theatmospheric air are partially integrated.

FIG. 7 shows the features of the embodiment. It is to be noted that thecomponents in FIG. 7 that are identical to those in the first embodimentare not explained.

A process gas supply device 200 is constituted of a chlorine-based gassupply system 208, gas outlet holes 134 a and the like. In theembodiment, an atmospheric air supply system 300 and a switching valve301 to be utilized to supply the atmospheric air present around theprocessing chamber into the processing chamber through the gas outletholes 134 a are connected to the chlorine-based gas supply system 208 ata specific position. It is to be noted that a mesh 302 may be providedat the atmosphere-side end of the atmospheric air supply system 300 tofunction as a filter that prevents entry of dust in the atmosphere intothe atmospheric air supply system 300.

During the actual chlorine-based gas removal process executed byadopting the structure described above, the air operation valves 154 and156 are first opened to reduce the pressure inside the processingchamber 102. As a sensor detects that the pressure inside the processingchamber 102 has been lowered to a predetermined level (approximately2Torr), the switching valve 301 is opened to let the atmospheric airinto the atmospheric air supply system 300. Since the pressure insidethe processing chamber has been lowered, the chlorine-based gas insidethe processing chamber is not released to the outside through theatmospheric air supply system and, instead, the atmospheric air presentaround the processing chamber travels through the atmospheric air supplysystem 300 and is supplied into the processing chamber through the gasoutlet holes 134 a.

The moisture in the atmospheric air supplied into the processing chamberreacts with the chlorine-based gas inside the processing chamber andproduces acid which is then evacuated through the acid evacuation line150.

By allowing the process gas supply device 200 to bypass the atmosphericair supply system 300, supplying the atmospheric air from theenvironment into the processing chamber through the atmospheric airsupply system 300 after lowering the pressure inside the processingchamber and evacuating the acid produced through the reaction of themoisture in the atmospheric air and the chlorine-based gas in theprocessing chamber as in the embodiment, the chlorine-based gas can beevacuated in a manner similar to that achieved in the first embodimentand furthermore, the chlorine-based gas evacuation is achieved through asimpler structure compared to the first embodiment. Moreover, since alarge drive system is not required, the chlorine-based gas removalsystem can be automated with ease.

(Third Embodiment)

The third embodiment of the present invention is now explained. Whilethe air supply device in the second embodiment is achieved by allowingthe process gas supply device 200 to bypass the atmospheric air supplysystem 300, in the third embodiment, the atmospheric air supply systemis made to directly connect the processing chamber to enable removal ofthe chlorine-based gas inside the processing chamber .

FIG. 8 shows the features of the embodiment. It is to be noted that thecomponents in FIG. 8 that are identical to those in the first embodimentare not explained.

As FIG. 8 clearly illustrates, an atmospheric air supply system 400 isdirectly connected at the external surface of the processing chamber 102in order to directly supply the atmospheric air present in the vicinityof the processing chamber into the processing chamber and a hole 403 isformed at the top of the processing chamber to allow the atmospheric airto flow from the atmospheric air supply system 400 into the processingchamber 102. The atmospheric air supply system 400 includes a switchingvalve 401. In addition, as in the second embodiment, a mesh 402 may beprovided at the atmosphere-side end of the atmospheric air supply system400 to function as a filter which prevents entry of dust in theatmosphere into the atmospheric air supply system 400.

During the actual chlorine-based gas removal process executed byadopting the structure described above, the air operation valves 154 and156 are first opened to reduce the pressure inside the processingchamber 102, as in the second embodiment. As a sensor detects that thepressure inside the processing chamber 102 has been lowered to apredetermined level (approximately 2Torr), the switching valve 401 isopened to let the atmospheric air into the atmospheric air supply system400. Since the pressure inside the processing chamber 102 has beenlowered, the chlorine-based gas inside the processing chamber 102 is notreleased to the outside through the atmospheric air supply system 400and, instead, the atmospheric air present in the environment travelsthrough the atmospheric air supply system 400 and through the hole 403formed at the processing chamber and is supplied into the processingchamber 102 through an atmospheric air outlet hole 404.

The moisture in the atmospheric air supplied into the processing chamberreacts with the chlorine-based gas inside the processing chamber andproduces acid which is then evacuated through the acid evacuation line150.

By allowing the atmospheric air supply system 400 to directly connect tothe processing chamber 102, providing the hole 403 and the atmosphericair outlet hole 404 at the processing chamber 102 supplying theatmospheric air around the processing chamber 102 into the processingchamber and evacuating the acid produced through the reaction of themoisture in the atmospheric air and the chlorine-based gas inside theprocessing chamber as in the embodiment, the chlorine-based gas can beevacuated as effectively as in the first embodiment. Furthermore, thechlorine-based gas evacuation can be achieved through a simplerstructure compared to the first embodiment. Moreover, since a largedrive system is not required, the chlorine-based gas removal system canbe automated with ease.

While the invention has been particularly shown and described withrespect to preferred embodiments of the halogen gas removal method andthe halogen gas removal system according to the present invention byreferring to the attached drawings, the present invention is not limitedto these examples and it will be understood by those skilled in the artthat various changes in form and detail may be made therein withoutdeparting from the spirit, scope and teaching of the invention.

As explained above, according to the present invention, in which thepressure inside the processing chamber is reduced to a level which is atleast lower than the atmospheric pressure (reduced to a negativepressure), the halogen gas is not allowed to become diffused to theoutside of the processing chamber when the atmospheric air is suppliedinto the processing chamber. As a result, the reaction product, i.e.,acid, resulting from the reaction of the supplied atmospheric air andthe gas present in the processing gas can be evacuated to achieve quickand reliable removal of the gas. In addition, since the pressure insidethe processing chamber is sustained at a negative level, there is noirritating odor of the gas and the gas leakage detector does not go offduring the subsequent maintenance work, thereby assuring safety of themaintenance personnel.

The present invention may be adopted in plasma processing executed byusing a halogen gas during the process of manufacturing, for instance,semiconductor devices.

1. A gas removal system, that removes a halogen gas remaining inside aprocessing chamber after executing processing inside said processingchamber in an airtight state and obtaining plasma through dischargedissociation of a process gas, which contains the halogen gas suppliedfrom a process gas supply system, comprising: a pressure control devicethat controls the pressure inside said processing chamber; an air supplydevice that supplies atmospheric air into said processing chamber afterlowering the pressure inside said processing chamber with said pressurecontrol device, wherein lowering pressure inside said processing chamberprevents diffusion of the halogen gas to an atmosphere outside saidprocessing chamber, wherein said air supply device comprises anatmosphere opening device that opens said processing chamber to anatmosphere outside of the processing chamber, wherein said atmosphereopening device comprises a rotating mechanism for rotating said processgas supply system; a control device that controls said air supplydevice; an evacuation device that evacuates a gas produced through areaction of the halogen gas and the atmospheric air having occurred insaid processing chamber; and a sensor that detects an extent to whichsaid processing chamber is opened to the atmosphere by said atmosphereopening device.
 2. A gas removal system according to claim 1, wherein:the extent to which said processing chamber is open to the atmosphere bysaid atmosphere opening device comprises a first degree at which saidprocessing chamber is not opened to the atmosphere at all, a seconddegree at which said processing chamber is opened to the atmosphere to apredetermined extent to remove the gas and a third degree at which saidprocessing chamber is completely open to the atmosphere; and said sensorcomprises a first sensor having a detection range from the first degreeto the second degree and a second sensor having a detection range fromthe second degree to the third degree.
 3. A gas removal system accordingto claim 2, wherein: said second degree is approximately 2% of saidthird degree.
 4. A gas removal system according to claim 2, wherein:said atmosphere opening device issues a warning if said first sensordetects that the extent to which said processing chamber is opened tothe atmosphere is the first degree before a predetermined length of timeelapses.
 5. A gas removal system according to claim 2, wherein: saidatmosphere opening device issues a warning if said second sensor detectsthat the extent to which said processing chamber is opened to theatmosphere is the third degree before a predetermined length of timeelapses.
 6. A gas removal system according to claim 1, wherein: saidhalogen gas is chlorine.
 7. A gas removal system according to claim 1,wherein: said halogen gas is hydrogen bromide.
 8. A plasma processingapparatus, that executes plasma processing on a workpiece placed insidea processing chamber, comprising: a pressure control device thatcontrols the pressure inside said processing chamber; an air supplydevice that supplies atmospheric air into said processing chamber afterlowering the pressure inside said processing chamber with said pressurecontrol device, wherein lowering pressure inside said processing chamberprevents diffusion of a halogen gas to an atmosphere outside saidprocessing chamber, wherein said air supply device comprises anatmosphere opening device that opens said processing chamber to anatmosphere outside of the processing chamber, wherein said atmosphereopening device comprises a rotating mechanism for rotating a process gassupply device; a control device that controls said air supply device;and an evacuation device that evacuates a gas produced through areaction of the halogen gas and the atmospheric air having occurred insaid processing chamber; and a sensor that detects an extent to whichsaid processing chamber is opened to the atmosphere by said atmosphereopening device.